We have developed a procedure for isolating amplified nucleoli from Xenopus oocytes. These nucleioli contain the genes coding for ribosomal RNA and are free of other contaminating bulk DNA. We are currently cataloguing the proteins associated with this single gene and intend to map their locations on the gene. BIBLIOGRAPHIC REFERENCES: Bokhon'ko, A. and Reeder, R.H., "The Subunit Structure of Mouse Satellite Chromatin", Biochem. Biophys. Res. Comm., 70, 146-152 (1976). Biroc, S.L. and Reeder, R.H., "Iodination of Xenopus laevis Histone F2al in Chromatin", Biochemistry 15, 1440-1448 (1976).